Many structures have pitched, shingled roofs, which prevent water, e.g., rain water, from entering the structures by causing water to pass over the shingles and off the roofs. A pitched, shingled roof has a pitched substrate, such a plurality of plywood sheets, with a plurality of shingles attached thereto.
Each shingle has an upper portion and a lower portion wherein the lower portion is exposed to the environment. The shingles are typically attached to the substrate in rows wherein the lower portions an upper row of shingles overlaps the upper portions of an adjacent lower row of shingles. For example, a first row of shingles may be attached to the substrate nearest the lowest point of the roof, i.e., the eave portion of the roof. A second row of shingles may then be attached to the substrate slightly higher on the roof than the first row. The shingles are placed so that the lower portions of the second row of shingles overlaps the upper portions of the first row of shingles. This overlapping continues with successive rows of shingles to the highest point on the roof. Thus, only the lower portions of the shingles are exposed to the environment. This overlapping of the shingles causes water to pass from shingles on a high row shingles to shingles on the next lowest row of shingles without contacting the substrate. Accordingly, water passes from shingle to shingle and off the roof without contacting the substrate or entering the structure.
Attaching the shingles to the roof is typically achieved by the use of nails or other fastening devices that pass through the shingles and into or through the substrate. The fastening devices are typically placed through the upper portions of the shingles so that they are overlapped by shingles in an adjacent higher row as described above. This placement of the fasteners prevents water from entering the structure through holes caused by the fasteners.
Some roofs have a membrane located between the substrate and the shingles. The membrane may, as an example, be conventional tar paper that is nailed to the substrate. The tar paper-type membrane is typically manufactured from a paper product and, thus, does not have a high degree of integrity. Strips of the membrane are typically attached to the roof in an overlapping fashion wherein an upper strip overlaps its adjacent lower strip. Accordingly, the membrane serves to shield the substrate from water should a shingle become damaged. For example, if a shingle becomes cracked or otherwise leaks, water will contact the membrane rather than the substrate. Water will then pass along the membrane to the next lowest shingle without contacting the substrate or entering the structure. Alternatively, water will pass along the membrane, under the shingles and off the roof. Many membranes, however, are susceptible to passing water to the substrate and into the structure. For example, when nails are used to attach the shingles to the substrate, the nails pass through the membrane and, accordingly, make holes in the membrane. In the event water contacts the membrane, these holes may allow water to pass through the substrate and into the structure.
Even with overlapping shingles and membranes as described above, conventional pitched, shingled roofs are susceptible to water leakage, which can damage their underlying structures. For example, if the membrane is damaged, i.e., it tears, it will not be able to shield the substrate from water. Thus, if a shingle in the proximity of the damaged membrane also becomes damaged, water will contact the substrate and may enter the underlying structure. Tar paper and similar membranes tend not be durable and further tend to tear when subjected to minimal force and are, accordingly, susceptible to leaking.
Another way for water to enter the underlying structure is by the formation of an ice dam on the roof. An ice dam forms when water flows down a roof and encounters a portion of the roof that is below freezing. When the water encounters the portion of the roof that is below freezing, it freezes and forms an ice sheet. As water continues to flow onto the portion of the roof that is below freezing, the ice sheet thickens and eventually forms a barrier or ice dam. The water on the relatively warm portion of the roof that is above freezing, does not freeze and accumulates as a pool of standing water. This standing water eventually seeps underneath the shingles. The water then encounters the substrate and may pass into the underlying structure. The aforementioned tar paper-type membranes generally do not seal the roof against standing water such as caused by an ice dam. For example, water standing behind the ice dam seeps under the shingles and between the strips of the membrane. The water may then contact the substrate and pass into the structure. In another example, the standing water may pass under the shingles and contact a nail hole in the membrane. The water may then follow the nail hole into the structure.
One of the causes of ice dams is due to melting snow caused by heat passing through the roof. The situation typically arises with a roof having an eave and an accumulation of snow located thereon when the outside air temperature is below freezing. An eave is a portion of the roof that extends horizontally beyond the underlying structure. Due to the cold outside air temperature, the interior of the underlying structure is heated. This causes heat to rise through the structure and heat the roof. Because the eave portion of the roof extends horizontally beyond the underlying structure, it will not be heated. The snow accumulation on the roof forms an insulating barrier between the heated roof and the cold outside air. When enough heat passes into the roof to raise the roof temperature above freezing, the snow adjacent the roof melts. The water from the melting snow passes down the roof under the snow and toward the eave portion of the roof. The eave portion, however, is below freezing because it is not heated by extraneous heat escaping from the underlying structure. Thus, when the water from the melting snow passes over the portion of the roof covering the eave, it freezes. As the snow continues to melt, more water passes over the eave portion of the roof and freezes. Eventually, ice builds up on the eave portion of the roof and forms a barrier or ice dam, which prevents water from running off the roof. The water then backs up on the roof and seeps under the shingles to the substrate. If there are any holes in the substrate, the water will pass through the holes and into the structure as described above.
When a roof is found to leak upon the formation of an ice dam, the most practical method of alleviating the leakage problem is to seal the substrate. Sealing the substrate, however, requires the removal of the shingles in order to access the substrate. The shingles typically cannot be salvaged and, accordingly, must be discarded. The substrate is then sealed and a new layer of shingles is attached to the substrate. This process is costly due to the cost of removing the existing shingles, the replacement cost for new shingles, and the disposal cost of the discarded shingles. In addition, the removal of the shingles may cause damage to the substrate, which must be repaired prior to the application of new shingles and further increases the cost of sealing the roof.
A waterproof membrane is typically used to seal the substrate. For example, a membrane may be adhered to the substrate to form a waterproof sheet on the substrate. Accordingly, water is prevented from contacting the substrate and entering the structure. Some roofs are constructed with such a waterproof membrane affixed to the substrate prior to the application of the shingles. Should the membrane become damaged for any reason, however, the roof may be susceptible to leaking upon the formation of an ice dam. The aforementioned process of removing the shingles to reseal the roof must then be performed. The process, however, has the additional burden of replacing the membrane, which may cause significant damage to the substrate if it is adhered to the substrate.
Therefore, a need exists for a method of sealing a roof that does not require removal of the existing roofing shingles.